On the possibility of a long range proximity effect in a ferromagnetic nanoparticle

TL;DR

This paper investigates the conditions under which a long-range superconducting proximity effect can occur in ferromagnetic nanoparticles, highlighting the role of symmetry breaking in enabling extended superconducting correlations.

Contribution

It demonstrates that perfect axial symmetry prevents long-range proximity effects, but symmetry breaking through vortex displacement or anisotropy can induce such effects.

Findings

Long-range proximity effect is absent in symmetric systems.

Symmetry breaking enables long-range superconducting correlations.

Localized superconductivity occurs near the electrode in symmetric cases.

Abstract

We study the proximity effect in a ferromagnetic nanoparticle having a vortex magnetization pattern. We show that for axisymmetric system consisting of a circular particle and a magnetic vortex situated at the center of it no long range superconducting correlations are induced. It means that induced superconductivity is localized in the small area near the superconducting electrode. However, in the real systems axial symmetry can be broken by either a shift of the magnetic vortex from the origin or geometrical anisotropy of the ferromagnetic particle. In this case a long range proximity effect is possible.